A rapid prediction method for explosion shock wave loads in ship cabins considering bulkhead shielding

Abstract

The present invention provides a method for quickly predicting the explosion shock wave load in a ship cabin taking into account the shielding of bulkheads. The method includes the following steps: step S1, discretization of the three-dimensional ship cabin structure model and equivalent charge conversion; step S2, division of the calculation step length; step S3, calculation of the pressure and damage state of each bulkhead; step S4, elimination of the bulkheads that are actually not damaged; step S5, calculation of the pressure load reduction of the damaged bulkhead; the present invention calculates the bulkhead load and damage state by solving the step length, which can greatly improve the calculation efficiency and reduce the calculation time for large-sized ship targets. The present invention constructs the explosion point and the geometric center ray of the bulkhead, and judges whether there is an undamaged wall shielding before the damaged bulkhead based on the cyclic scanning method, thereby eliminating the bulkheads that will not actually be damaged, making the calculation results more realistic.

Description

Technical Field

[0001] The present invention belongs to the technical field of damage assessment, relates to a ship cabin, and in particular to a method for quickly predicting explosion shock wave loads in a ship cabin taking bulkhead shielding into consideration. Background Art

[0002] The penetration of anti-ship missiles into the ship's cabin and explosion is one of the typical combat scenarios. Due to the constraint of the bulkhead structure, the shock wave load after the explosion is constantly reflected, converged and superimposed in the space, which makes the calculation of the internal explosion load very complicated; at the same time, due to the shielding effect of each bulkhead, whether the adjacent cabin structure will be subjected to pressure load, or how much pressure load it will be subjected to, and whether it has been damaged are all important bases for conducting damage assessment. Therefore, establishing a rapid prediction method for the shock wave load of the explosion in the ship's cabin that can take into account the shielding of the bulkhead is of great significance for evaluating the strike effect of anti-ship missiles on ship targets.

[0003] At present, the prediction of internal explosion loads can be mainly divided into two methods: engineering semi-empirical and finite element numerical simulation. For example, Baker et al. proposed a simplified prediction model of three-wave peaks for explosions in spherical containers, pointing out that the second and third reflection peaks are approximately 1 / 2 and 1 / 4 of the first peak, respectively; Yang Yadong et al. used the mirror explosion source method to establish an analysis model for the propagation and superposition of explosion shock waves in a rectangular closed structure; Chen Pengyu et al. established a simplified calculation model for the load on the target wall under the explosion load in a single cabin; Yao Di et al. used MSC.Dytran software to analyze the propagation and convergence laws of explosion shock waves in typical cabin structures; Gu Hongping et al. used LS-DYNA to analyze the load similarity law of internal explosion pressure peak and impulse; Xu Weizheng et al. used a self-developed high-precision three-dimensional numerical calculation program for internal explosions to carry out research on the distribution characteristics of explosion overpressure loads in confined spaces.

[0004] Based on the above analysis, it can be seen that the finite element numerical simulation calculation method can better predict the pressure distribution of explosives in the cabin during the explosion process and its destructive effect on the bulkhead structure, but its disadvantages are that the calculation is time-consuming and has high requirements for computing hardware, especially for the actual ship target size, which is usually above 100 meters. The calculation time of a single explosion point is usually more than dozens of hours, which is not suitable for actual rapid evaluation needs; and the existing engineering semi-empirical prediction method can only predict the pressure load of the cabin, but cannot predict the pressure of the cabin, and also does not consider the shielding and reduction effect of the bulkhead structure on the shock wave load. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a method for quickly predicting the explosion shock wave load in a ship cabin taking into account the shielding of the bulkhead, so as to solve the technical problem that in the existing rapid calculation process of the explosion shock wave load in the ship cabin, the shielding of the actual bulkhead structure load cannot be taken into account.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0007] A method for quickly predicting explosion shock wave loads in a ship cabin taking into account bulkhead shielding, the method comprising the following steps:

[0008] Step S1, discretization of the three-dimensional ship cabin structure model and conversion of equivalent dose:

[0009] Firstly, the three-dimensional ship cabin entity structure is degraded, and the discrete thin shell unit is used to replace the model of each bulkhead structure. The size of the three-dimensional ship cabin structure model is consistent with the actual size of the ship target, and the position where each bulkhead is connected in the actual structure is processed by collinearity to ensure the closure of the cabin structure.

[0010] Secondly, the equivalent TNT charge mass of the explosive W e It can be converted according to formula I:

[0011] Formula I;

[0012] Where:

[0013] W is the actual charge mass of explosive;

[0014] Q e for the detonation heat of the actual explosive;

[0015] Q The explosive heat of TNT explosives;

[0016] Step S2, divide the calculation step size:

[0017] Count all bulkheads to the explosion point ( x 0 , y 0 , z 0 ) distance, according to the coordinates of all the facet nodes contained in each bulkhead, the geometric center ( x ci , y ci , z ci ) solution calculation;

[0018] Formula II;

[0019] The distance from the geometric center of each bulkhead to the explosion point Calculate according to formula III:

[0020] Formula III;

[0021] Based on the distance between all bulkheads and the explosion point d ci , calculate the minimum value d ci_min and maximum value d ci_max ,in accordance with( d ci_max - d ci_min - d 0 ) Determine the number of calculation steps n , and use this to determine the calculation step size: Δ( d ci_max - d ci_min - d 0 ) / n ;

[0022] Where:

[0023] x i , y i , z i are the three-dimensional coordinates of all the discretized subdivision surface element nodes contained in the bulkhead;

[0024] i Number the nodes of the discretized subdivision surface element;

[0025] n is the number of steps;

[0026] d c is the distance between two points;

[0027] d 0 is the selected initial calculation distance;

[0028] Step S3, calculate the pressure and damage state of each bulkhead:

[0029] according to d 0 +Δ( d ci_max - d ci_min- d 0 ) / n × i , i=0,1,2…n , calculate the reflected pressure of each point on the wall of all cabins within the step range in turn, and calculate according to formula IV:

[0030] Formula IV;

[0031] Where:

[0032] α V and α H are the angles between the line connecting the “explosion point-measurement point” and the two vertical planes of the bulkhead;

[0033] Δ p ref is the positive reflection pressure of the shock wave at the projection of the explosion point on the bulkhead plane;

[0034] Δ p ref Calculate according to formula V;

[0035] Formula V;

[0036] Where:

[0037] W e is the equivalent TNT charge mass of the explosive calculated by formula Ⅰ, in kg;

[0038] r cic The distance between the explosion point and the nearest point on the bulkhead, in meters, is calculated from the shortest distance from a spatial point to a plane.

[0039] p 0 is the ambient pressure, which is 0.101MPa;

[0040] according to d 0 +Δ( d ci_max - d ci_min - d 0 ) / n × i , i=0,1,2…n , calculate the damage of all cabin walls within the step range in turn, and the judgment basis is r cic Less than the critical explosion distance that causes damage to the bulkhead structure d cic ,d cic It can be calculated by formula VI:

[0041] Formula VI;

[0042] Where:

[0043] h is the equivalent thickness of the bulkhead, in m;

[0044] ρ is the bulkhead structural material density, unit: kg / m 3 ;

[0045] σ d is the dynamic yield strength of the bulkhead structural material, unit: Pa;

[0046] ε f is the fracture strain of the bulkhead structural material;

[0047] Step S4, remove the bulkheads that are actually not damaged:

[0048] Count all destroyed bulkhead structures and build them one by one from the explosion point ( x 0 , y 0 , z 0 ) to the geometric center of each destroyed bulkhead [( x d1 , y d1 , z d1 ), ( x d2 , y d2 , z d2 ),…,( x di , y di , z di )] space ray:

[0049] Formula VII;

[0050] Where:

[0051] x, y, z The variables for constructing the equation of the line in space respectively;

[0052] The ray is intersected with all the target cabin walls, and all the cabin walls that the ray passes through on its path are counted. The statistical method is to first calculate the intersection point of the spatial straight line and the cabin wall plane, and then confirm that the intersection point is within the cabin wall plane;

[0053] A little space P Not in the convex polygonal plane A ( a 1 , a 2 ,..., a k The necessary and sufficient conditions in formula VIII are:

[0054] Formula VIII;

[0055] in:

[0056] is a triangle;

[0057] a 1 , a 2 ,..., a k is the convex polygonal plane A 1 , 2 ,..., k vertices;

[0058] i The ordinal number of the vertex;

[0059] Count the penetration paths of the ray before it intersects the bulkhead plane, determine how many other bulkheads there are on the path, and determine whether there are undamaged walls. If there are, it means that the current wall will be blocked by the undamaged wall, so the bulkhead is removed from the damaged wall set;

[0060] Step S5, calculate the pressure load reduction for destroying the bulkhead:

[0061] Since the actual destruction of the cabin wall will consume part of the explosion shock wave energy, after counting all the damaged cabin walls, the number of remaining walls destroyed from the explosion point to the geometric center of the wall is calculated. n f When calculating the shock wave load, it is necessary to multiply the reduction factor based on Formula IV. P dis , the reduction factor P dis Obtained by formula IX;

[0062] Formula IX.

[0063] The present invention also has the following technical features:

[0064] In step S4, step S4 is repeated according to the divided step length during calculation until all the bulkheads within the step length are not damaged, and then the step can be stopped.

[0065] In step S5, step S5 is repeated during calculation until all connecting lines and all destroyed bulkhead planes are calculated and the step is terminated.

[0066] Compared with the prior art, the present invention has the following technical effects:

[0067] (I) The present invention calculates the bulkhead load and damage state by solving the problem in a step-by-step manner, which can greatly improve the calculation efficiency and reduce the calculation time for large-sized ship targets.

[0068] (II) The present invention constructs the explosion point and the geometric center ray of the bulkhead, and judges whether there is an undamaged wall surface blocking the damaged bulkhead based on the circular scanning method, thereby eliminating the bulkhead that will not be damaged in reality, making the calculation result more realistic.

[0069] (III) The present invention establishes a rapid calculation method for the cabin wall shock wave load under the condition of shielding the wall, which is mainly based on engineering semi-empirical calculation formulas, has a simple form, is easy to solve, and has high operation and solution efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 It is a schematic diagram of a model of a certain compartment of a ship target after the structural surface element is discretized in an embodiment of the present invention.

[0071] Figure 2 The figure is a schematic diagram of the calculation step division when looking down at a cabin structure according to an embodiment of the present invention.

[0072] Figure 3 Schematic diagram of a method for calculating wall shock wave load at any measuring point in an embodiment of the present invention.

[0073] Figure 4 Schematic diagram of the principle of removing blocked but undamaged bulkheads in an embodiment of the present invention.

[0074] Figure 5 The present invention provides an example of pressure distribution and damage at a typical position of a structural section of a certain compartment of a target ship under the action of an internal explosion of a certain amount of TNT explosive, calculated using the method and steps described in the embodiments of the present invention.

[0075] The specific contents of the present invention are further explained in detail below in conjunction with embodiments. DETAILED DESCRIPTION

[0076] It should be noted that, unless otherwise specified, all devices in the present invention are devices known in the prior art.

[0077] The present invention proposes a method for quickly predicting the shock wave load of explosions in ship cabins taking into account the shielding of bulkheads. The method uses a step-by-step calculation method to establish a shock wave pressure calculation method for any point on the bulkhead structure, and eliminates the wall surface that is not actually damaged by constructing a shooting line. At the same time, the coefficient reduction of the shock wave load caused by the wall damage is considered. The load calculation method of the present invention has clear steps, a simple form, high efficiency, and is more in line with the actual situation. It solves the problem that the shielding of the actual bulkhead structure load cannot be considered in the existing rapid calculation process of the shock wave load engineering of the explosion in the ship cabin, and provides technical support for the rapid damage assessment of ship-type targets.

[0078] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0079] Embodiment 1:

[0080] This embodiment provides a method for quickly predicting explosion shock wave loads in a ship cabin taking into account bulkhead shielding. The method includes the following steps:

[0081] Step S1, discretization of the three-dimensional ship cabin structure model and conversion of equivalent dose:

[0082] Firstly, the three-dimensional ship cabin entity structure is degraded, and the discrete thin shell unit is used to replace the model of each bulkhead structure. The size of the three-dimensional ship cabin structure model is consistent with the actual size of the ship target, and the position where each bulkhead is connected in the actual structure is processed by collinearity to ensure the closure of the cabin structure.

[0083] Specifically, in this embodiment, each bulkhead can be composed of one or more discrete 3- or 4-node subdivision facets. The finer the discreteness, the more wall reflection pressure values ​​calculated, the more continuous the pressure distribution cloud map obtained, and the better the effect. The size of the discrete model is consistent with the actual size of the ship target, such as Figure 1 The figure shows the discretized model of a certain compartment structure of a certain type of ship target. The locations where the bulkheads are connected in the actual structure are processed in a collinear manner in the discrete model to ensure the closure of the compartment structure.

[0084] Secondly, the equivalent TNT charge mass of the explosive W e It can be converted according to formula I:

[0085] Formula I;

[0086] Where:

[0087] W is the actual charge mass of explosive;

[0088] Q e for the detonation heat of the actual explosive;

[0089] Q The explosive heat of TNT explosives;

[0090] Step S2, divide the calculation step size:

[0091] In this embodiment, considering that the ship target is usually large in scale, in order to save calculation time, the damage of the bulkhead is calculated according to the step length.

[0092] Count all bulkheads to the explosion point ( x 0 , y 0 , z 0 ) distance, according to the coordinates of all the facet nodes contained in each bulkhead, the geometric center ( x ci , y ci , z ci ) solution calculation;

[0093] Formula II;

[0094] The distance from the geometric center of each bulkhead to the explosion point Calculate according to formula III:

[0095] Formula III;

[0096] Based on the distance between all bulkheads and the explosion point d ci , calculate the minimum value d ci_min (bulkhead closest to the explosion point) and the maximum d ci_max (the bulkhead farthest from the explosion point), according to ( d ci_max - d ci_min - d 0 ) Determine the number of calculation steps n , and use this to determine the calculation step size: Δ( d ci_max - d ci_min - d 0 ) / n ;

[0097] Where:

[0098] x i , y i , z i are the three-dimensional coordinates of all the discretized subdivision surface element nodes contained in the bulkhead;

[0099] i Number the nodes of the discretized subdivision surface element;

[0100] n is the number of steps;

[0101] d c is the distance between two points;

[0102] d 0 is the selected initial calculation distance;

[0103] In this embodiment, the calculation step length division diagram of the embodiment is as follows Figure 2 shown.

[0104] In step S2, the number n of steps can be determined according to demand and computer performance. The larger the number, the more accurate the calculation result.

[0105] Step S3, calculate the pressure and damage state of each bulkhead:

[0106] like Figure 3 As shown, press d 0 +Δ( d ci_max - d ci_min - d 0 ) / n × i , i=0,1,2…n , calculate the reflected pressure of each point on the wall of all cabins within the step range in turn, and calculate according to formula IV:

[0107] Formula IV;

[0108] Where:

[0109] α V and α H are the angles between the line connecting the “explosion point-measurement point” and the two vertical planes of the bulkhead;

[0110] Δp ref is the positive reflection pressure of the shock wave at the projection of the explosion point on the bulkhead plane;

[0111] Δ p ref Calculate according to formula V;

[0112] Formula V;

[0113] Where:

[0114] W e is the equivalent TNT charge mass of the explosive calculated by formula Ⅰ, in kg;

[0115] r cic The distance between the explosion point and the nearest point on the bulkhead, in meters, is calculated from the shortest distance from a spatial point to a plane.

[0116] p 0 is the ambient pressure, which is 0.101MPa;

[0117] according to d 0 +Δ( d ci_max - d ci_min - d 0 ) / n × i , i=0,1,2…n , calculate the damage of all cabin walls within the step range in turn, and the judgment basis is r cic Less than the critical explosion distance that causes damage to the bulkhead structure d cic , d cic It can be calculated by formula VI:

[0118] Formula VI;

[0119] Where:

[0120] h is the equivalent thickness of the bulkhead, in m;

[0121] ρ is the bulkhead structural material density, unit: kg / m 3 ;

[0122] σ d is the dynamic yield strength of the bulkhead structural material, unit: Pa;

[0123] ε f is the fracture strain of the bulkhead structural material;

[0124] Step S4, remove the bulkheads that are actually not damaged:

[0125] Count all destroyed bulkhead structures and build them one by one from the explosion point ( x 0 , y 0 , z 0 ) to the geometric center of each destroyed bulkhead [( x d1 , y d1 , z d1 ), ( x d2 , y d2 , z d2 ),…,( x di , y di , z di )] space ray:

[0126] Formula VII;

[0127] Where:

[0128] x, y, z The variables for constructing the equation of the line in space respectively;

[0129] The ray is intersected with all the target cabin walls, and all the cabin walls that the ray passes through on its path are counted. The statistical method is to first calculate the intersection point of the spatial straight line and the cabin wall plane, and then confirm that the intersection point is within the cabin wall plane;

[0130] A little space P Not in the convex polygonal plane A ( a 1 , a 2 ,..., a k The necessary and sufficient conditions in formula VIII are:

[0131] Formula VIII;

[0132] in:

[0133] is a triangle;

[0134] a 1 , a 2 ,..., a k is the convex polygonal plane A 1 , 2 ,..., k vertices;

[0135] i The ordinal number of the vertex;

[0136] The penetration path before the ray intersects the bulkhead plane is counted to determine how many other bulkheads there are on the path and whether there are any undamaged walls. If so, it means that the current wall will be blocked by the undamaged wall, so the bulkhead is removed from the damaged wall set. Figure 4 shown.

[0137] In step S4, step S4 is repeated according to the divided step length during calculation until all the bulkheads within the step length are not damaged, and then the step can be stopped.

[0138] Step S5, calculate the pressure load reduction for destroying the bulkhead:

[0139] Since the actual destruction of the cabin wall will consume part of the explosion shock wave energy, after counting all the damaged cabin walls, the number of remaining walls destroyed from the explosion point to the geometric center of the wall is calculated. n f When calculating the shock wave load, it is necessary to multiply the reduction factor based on Formula IV. P dis , the reduction factor P dis Obtained by formula IX;

[0140] Formula IX.

[0141] In step S5, step S5 is repeated during calculation until all connecting lines and all destroyed bulkhead planes are calculated and the step is terminated.

[0142] like Figure 5 As shown, it is an example of pressure distribution at a typical position of a section structure of a certain ship target and bulkhead damage under the action of 70kgTNT internal explosion calculated by the method and steps described in the embodiment of the present invention, which verifies the feasibility of the method proposed in the present invention.

Claims

1. A method for rapid prediction of explosion shock wave load in a ship cabin considering bulkhead shielding, characterized in that: The method comprises the following steps: Step S1, discretization of the three-dimensional ship cabin structure model and conversion of equivalent dose: Firstly, the three-dimensional ship cabin entity structure is degraded, and the discrete thin shell unit is used to replace the model of each bulkhead structure. The size of the three-dimensional ship cabin structure model is consistent with the actual size of the ship target, and the position where each bulkhead is connected in the actual structure is processed by collinearity to ensure the closure of the cabin structure. Secondly, the equivalent TNT charge mass of the explosive W e It can be converted according to formula I: Formula I; Where: W is the actual charge mass of explosive; Q e for the detonation heat of the actual explosive; Q The explosive heat of TNT explosives; Step S2, divide the calculation step size: Count all bulkheads to the explosion point ( x 0, y 0, z 0), according to the coordinates of all the facet nodes contained in each bulkhead, the geometric center ( x ci , y ci , z ci ) solution calculation; Formula II; The distance from the geometric center of each bulkhead to the explosion point Calculate according to formula III: Formula III; Based on the distance between all bulkheads and the explosion point d ci , calculate the minimum value d ci_min and maximum value d ci_max ,in accordance with( d ci_max - d ci_min - d 0) Determine the number of calculation steps n , and use this to determine the calculation step size: Δ( d ci_max - d ci_min - d 0) / n ; Where: x i , y i , z i are the three-dimensional coordinates of all the discretized subdivision surface element nodes contained in the bulkhead; i Number the nodes of the discretized subdivision surface element; n is the number of steps; d c is the distance between two points; d 0 is the selected initial calculation distance; Step S3, calculate the pressure and damage state of each bulkhead: according to d 0+Δ( d ci_max - d ci_min - d 0) / n × i , i =0,1,2… n , calculate the reflected pressure of each point on the wall of all cabins within the step range in turn, and calculate according to formula IV: Formula IV; Where: α V and α H are the angles between the line connecting the "explosion point-measurement point" and the two vertical planes of the bulkhead; Δ p ref is the positive reflection pressure of the shock wave at the projection of the explosion point on the bulkhead plane; Δ p ref Calculate according to formula V; Formula V; Where: W e is the equivalent TNT charge mass of the explosive calculated by formula Ⅰ, in kg; r cic The distance between the explosion point and the nearest point on the bulkhead, in meters, is calculated from the shortest distance from a spatial point to a plane. p 0 is the ambient pressure, which is 0.101MPa; according to d 0+Δ( d ci_max - d ci_min - d 0) / n × i , i =0,1,2… n , calculate the damage of all cabin walls within the step range in turn, and the judgment basis is r cic Less than the critical explosion distance that causes damage to the bulkhead structure d cic , d cic It can be calculated by formula VI: Formula VI; Where: h is the equivalent thickness of the bulkhead, in m; ρ is the bulkhead structural material density, unit: kg / m 3 ; σ d is the dynamic yield strength of the bulkhead structural material, unit: Pa; ε f is the fracture strain of the bulkhead structural material; Step S4, remove the bulkheads that are actually not damaged: Count all destroyed bulkhead structures and build them one by one from the explosion point ( x 0, y 0, z 0) to the geometric center of each destroyed bulkhead [( x d1 , y d1 , z d1 ), ( x d2 , y d2 , z d2 ),…,( x di , y di , z di )] space ray: Formula VII; Where: x, y, z The variables for constructing the equation of the line in space respectively; The ray is intersected with all the target cabin walls, and all the cabin walls that the ray passes through on its path are counted. The statistical method is to first calculate the intersection point of the spatial straight line and the cabin wall plane, and then confirm that the intersection point is within the cabin wall plane; A little space P Not in the convex polygonal plane A ( a 1, a 2,..., a k The necessary and sufficient conditions in formula VIII are: Formula VIII; in: is a triangle; a 1, a 2,..., a k is the convex polygonal plane A 1 , 2 ,..., k vertices; i is The ordinal number of the vertex; Count the penetration paths of the ray before it intersects the bulkhead plane, determine how many other bulkheads there are on the path, and determine whether there are undamaged walls. If there are, it means that the current wall will be blocked by the undamaged wall, so the bulkhead is removed from the damaged wall set; Step S5, calculate the pressure load reduction for destroying the bulkhead: Since the actual destruction of the cabin wall will consume part of the explosion shock wave energy, after counting all the damaged cabin walls, the number of remaining walls destroyed from the explosion point to the geometric center of the wall is calculated. n f When calculating the shock wave load, it is necessary to multiply the reduction factor based on Formula IV. P dis , the reduction factor P dis Obtained by formula IX; Formula IX.

2. The method for rapid prediction of explosion shock wave load in a ship cabin considering bulkhead shielding according to claim 1 is characterized in that: In step S4, step S4 is repeated according to the divided step length during calculation until all the bulkheads within the step length are not damaged, and then the step can be stopped.

3. The method for rapid prediction of explosion shock wave load in a ship cabin considering bulkhead shielding as claimed in claim 1 is characterized in that: In step S5, step S5 is repeated during calculation until all connecting lines and all destroyed bulkhead planes are calculated and the step is terminated.

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